One of the most common consequences of rattlesnake bite for which there is no effective treatment is myonecrosis. We have isolated from rattlesnake (Crotalus viridis viridis) venom a small, basic protein which induces vacuolation and subsequent death of skeletal muscle cells upon injection into mice. Light and electron microscopic examination of the muscle at various times after injection revealed a series of degenerative events comparable to those which occur after injection of the crude venom. We have recently prepared in rabbits an antiserum which is specific to the myotoxin. Experiments using the Ouchterlony agar-gel double diffusion technique demonstrated the presence of the myotoxin in crude C. viridis viridis venom and of an immunologically similar molecule in C. durissus terrificus venom. Antibody to the myotoxin was absent from commercial antivenin, routinely used to treat snakebite cases. The objectives of the proposed research are to determine the ability of anti-myotoxin serum to prevent myonecrosis from occurring after injection of the purse myotoxin and of the crude C. viridis viridis venom. A light microscopic assay will be used in which the number of vacuolated cells in a given area will be counted. This method will provide quantitative information on the extent of the myonecrosis produced by toxin alone, by toxin mixed with anti-myotoxin serum, and by injection of toxin followed by injection of anti-myotoxin serum. A randomized block design will be used in which the experimental unit will be a mouse and treatments will consist of various combinations of doses and time between injection and sampling. If antiserum to the pure myotoxin does prevent myonecrosis from occurring after injection of crude rattlesnake venom, then this would demonstrate one way in which treatment of snakebite-induced muscle necrosis could be improved.